I took three top engines, and an oldie, Shredder 6PB from 2002. If BF is the branching factor, then 1/Log(BF) is proportional to the depth the engine searches.

**Houdini 3**

Ply:15 Positions: 30 Avg Nodes: 4474464 Branching = 1.54

Ply:16 Positions: 30 Avg Nodes: 9993292 Branching = 2.23

Ply:17 Positions: 30 Avg Nodes:16583899 Branching = 1.66

Ply:18 Positions: 30 Avg Nodes:29529725 Branching = 1.78

Ply:19 Positions: 30 Avg Nodes:59452946 Branching = 2.01

Ply:20 Positions: 30 Avg Nodes:100502642 Branching = 1.69

Ply:21 Positions: 30 Avg Nodes:226412605 Branching = 2.25

Average BF:

**1.86**

1/Log(BF)=1.61

**Stockfish 3**

Ply:17 Positions: 30 Avg Nodes: 5738272 Branching = 1.51

Ply:18 Positions: 30 Avg Nodes: 9495564 Branching = 1.65

Ply:19 Positions: 30 Avg Nodes:14927319 Branching = 1.57

Ply:20 Positions: 30 Avg Nodes:25380846 Branching = 1.70

Ply:21 Positions: 30 Avg Nodes:37913346 Branching = 1.49

Ply:22 Positions: 30 Avg Nodes:58287426 Branching = 1.54

Ply:23 Positions: 30 Avg Nodes:105041456 Branching = 1.80

Average BF:

**1.61**

1/Log(BF)=2.10

**Komodo 5 CCT**

Ply:15 Positions: 30 Avg Nodes: 3132997 Branching = 1.74

Ply:16 Positions: 30 Avg Nodes: 5471869 Branching = 1.75

Ply:17 Positions: 30 Avg Nodes: 9833793 Branching = 1.80

Ply:18 Positions: 30 Avg Nodes:16946370 Branching = 1.72

Ply:19 Positions: 30 Avg Nodes:28120847 Branching = 1.66

Ply:20 Positions: 30 Avg Nodes:57150190 Branching = 2.03

Ply:21 Positions: 30 Avg Nodes:93519346 Branching = 1.64

Average BF:

**1.76**

1/Log(BF)=1.77

**Shredder 6**

Ply: 8 Positions: 30 Avg Nodes: 515591 Branching = 2.68

Ply: 9 Positions: 30 Avg Nodes: 1347856 Branching = 2.61

Ply:10 Positions: 30 Avg Nodes: 3997429 Branching = 2.97

Ply:11 Positions: 30 Avg Nodes: 8540293 Branching = 2.14

Ply:12 Positions: 30 Avg Nodes:19868716 Branching = 2.33

Ply:13 Positions: 30 Avg Nodes:51275681 Branching = 2.58

Ply:14 Positions: 30 Avg Nodes:119957110 Branching = 2.34

Average BF:

**2.51**

1/Log(BF)=1.09